Flanged gear pump

ABSTRACT

The invention concerns a gear pump with a pump body closed with a cover forming a cavity in which is provided a drive pinion, a driven pinion whose teeth cooperate with the drive pinion teeth, and two end shields arranged on either side of the driven pinion penetrating into a cavity provided in the pump body and the cover respectively, pressure being exerted on the outer surface of the end shields. The end shields each consist of a disc integral with one end of the driven pinion, the discs and the driven pinion being concentric, the discs covering the teeth of the driven pinion. The pressure exerted on the outer surface of the discs prevents them from being deformed such that practically no axial leakage zone is formed. Additionally, the discs can serve as guiding axis for the rotation of the driven pinion.

[0001] The present invention concerns a gear pump comprising a pump bodyclosed by a cover forming a cavity in which is located a driving pinioncapable of being driven in rotation by a driving shaft to which it isfixed, a driven pinion whose teeth cooperate with the teeth of thedriving pinion so as to be driven in rotation by the driving pinion, andtwo flanges located on both sides of the driven pinion protruding into acavity provided therefor in the pump body and the cover respectively,means being provided for applying a pressure to the external face of theflanges.

[0002] Such pumps are often used, in particular as oil, gas, or dieseloil pumps. Their major drawback is that the cover is susceptible todeform under the pressure existing in the discharge zone, which causesan axial play of the loose pinion. The deformation of the cover causes aleakage zone between the discharge and aspiration, so that the volumeoutput of the pump is lowered.

[0003] Numerous documents (FR 1 239 211 A, U.S. Pat. No. 3,046,902 A, DE11 72 959 B, GB 661 772 A, and GB 1 067 552 A) have proposed to disposebetween the pinions and the casing four sliding sleeves equipped withrecesses for the pinion axes. A function of these sleeves is to make thepump leak-tight by supporting the pinions. To this effect, the externalfaces of the sleeves are subjected to a determined pressure. In thefirst document, the external faces are subjected to the entry pressureof the pump, so that the risk of a reflux between the lateral faces ofthe pinions and the sleeves is not excluded, since the pressure existingin the discharge zone is higher than the pressure exerted on thesleeves. In the four other documents, the external faces are subjectedat least in part to the exit pressure. These sleeves have a circularshape corresponding approximately to the diameter of the pinions with aflat area corresponding to the median plane between the two pinions.These sleeves are thus blocked in rotation. Further, the flat areasarranged by pairs form a junction in the area of the median planebetween the two pinions, at the location where the risk of backflow isthe most important.

[0004] These pumps are complicated and require a precise adjusting ofthe various parts, which makes them costly and fragile.

[0005] An objective of the invention is thus to develop a pump of thetype of the pump presented in introduction whose cover is not at risk ofdeforming under the pressure and has a simpler design.

[0006] This objective is attained by the pump according to the inventionin which the flanges are constituted each by a disc integral with an endof the driven pinion, the discs and the driven pinion being concentric,the discs covering the teeth of the driven pinion. Thus, the flangesrotate at the same time as the driven pinion. Only the driven pinion isequipped with flanges that cover its teeth, which makes the pumpsaccording to the present invention simpler to manufacture. The pressureexerted on the external face of the discs which act as flanges preventthem from deforming so that practically no axial leakage zone is formedbetween the aspiration and the discharge as is the case in simple gearpumps. In addition, the whole zone where the teeth mesh is covered bythe discs, so that no junction along the median plane between thepinions is susceptible to cause a leak. Further, the discs hem in theteeth of the pinion, which prevents an axial play of the pinions. Thevolume output of the pump is thus improved. The discs can have adiameter larger than the external diameter of the pinion, although thisis not required.

[0007] In a preferred embodiment of the invention, the flanges act asguides for the rotation of the driven pinion. It is thus not required tohave, in addition to the flanges, a guiding shaft, such as those withwhich pumps of the state of the art are equipped.

[0008] According to the invention, the means for exerting a pressure onthe external faces of the discs comprise a first and a second space,located between the external face of the discs and the bottom of thecavity provided in the pump body and in the cover, respectively, and inwhich are applied approximately identical pressures. To simplify thegear pump, it is preferable that a canal crosses the driven pinion fromone end to the other so that the first and second spaces communicatewith each other. It is thus ensured that the two discs are subjected tothe same pressure. Similarly, it is preferable that the first and secondspaces are made to communicate with the discharge zone of the pump. Tothis effect, it is possible to design a canal or a groove thatcommunicates with the discharge zone and at least one of the spaces.

[0009] In a preferred embodiment, the discs are hollowed out to saveweight.

[0010] The invention will be described more in details below inreference to the drawings in which:

[0011]FIG. 1 is a longitudinal cross-section view of a gear pump;

[0012]FIG. 2 is a transverse cross-section view of a gear pump accordingto the state of the art with a deformed cover;

[0013]FIG. 3 is a transverse cross-section view of a gear pump accordingto the invention.

[0014] The gear pump according to the invention is constituted mainly bya pump body (2) closed by a cover (3) having a main cavity in which arelocated two pinions (4, 5) whose teeth cooperate with each other. Thefirst pinion (4), the driving pinion, is driven by a driving shaft (1).As soon as the driving pinion (4) rotates, it drives the second pinion(5), the driven pinion. The pump has an aspiration zone on one side anda discharge zone on the other side. Under the effect of the pressuredifference between the discharge zone and the aspiration zone and of therotation of the teeth, the cover of simple pumps tends to deform, asshown on FIG. 2. There appears in that case an axial leakage zone (6)between the discharge zone and the aspiration zone, which reduces thevolume output of the pump and increases the axial play of the pinions.The normal circulation of the fluid in the pump is shown on FIG. 1 inthe form of thick arrows, while the fluid reflux due to the axialleakage is shown by thinner arrows.

[0015] To avoid this problem, the gear pump according to the inventionis equipped with a driven pinion (5) reinforced by discs (8). At eachend of the driven pinion (5) is located a disc (8) integral with thepinion and which protrudes in a cavity (10) provided to this effect inthe pump body (2) and in the cover (3), respectively. A space isprovided between the external surface of the discs and the bottom of thecavity in which they protrude. The diameter of the discs corresponds tothe diameter of the pinion, taking into account tolerances. Thus, theteeth of the driving pinion (4) are hemmed in by the discs (8) in thesensitive zone of the gear. The pressure exerted on the external face ofthe discs (8) prevents any deformation of the discs. This ensuresfluid-tightness between the discharge zone and the aspiration zone.Indeed, no junction along the median plane between the pinions issusceptible of causing a leak, contrary to the pumps according to thestate of the art. In addition, only the driven pinion (5) is equippedwith flanges (8), which makes the pump according to the inventionsimpler and thus less expensive to manufacture.

[0016] Further, since the discs (8) are integral with the driven pinion(5), they ensure fluid-tightness even when the pressure exerted on theexternal faces of the discs (8) is still low, in particular when thepump is started.

[0017] The discs also fulfill a function as guiding shafts of the drivenpinion (5), so that it is also possible to eliminate such a shaft, whichis not the case with pumps according to the state of the art, where theflanges cannot rotate because of their very shape.

[0018] To ensure an identical pressure on both discs, a canal (9) thatcommunicates with both cavities (10) of the discs (8) is provided.

[0019] The pressure existing on the external face of the discs (8) isexerted by the pumped fluid thanks to the communication not shown of thecavities (10) with the discharge zone. This communication can beprovided in the form of a canal or a groove.

[0020] The discs (8) are made integral with the driven pinion byappropriate means (7). In order to save weight, it is preferable thatthe external surface of the discs (8) is hollowed out.

[0021] Thanks to the important reduction of plays, and thus theconsiderable reduction of leakage between the discharge zone and theaspiration zone, the volume output of the pump according to theinvention is improved. Further, the discs ensure an improved stabilityof the pinions, which also reduces their play.

List of Reference Numerals:

[0022]1 driving shaft

[0023]2 pump body

[0024]3 cover

[0025]4 driving pinion

[0026]5 driven pinion

[0027]6 leakage zone

[0028]7 fixing means of the disc

[0029]8 discs

[0030]9 canal

[0031]10 cavities

1. Gear pump, comprising a pump body closed by a cover forming a cavityin which are located a driving pinion capable of being driven inrotation by a driving shaft to which it is fixed a driven pinion whoseteeth cooperate with the teeth of the driving pinion so that the drivenpinion can be driven in rotation by the driving pinion and two flangeslocated on both sides of the driven pinion protruding into a cavityprovided to this effect in the pump body and the cover, respectively,means being provided for exerting a pressure on the external faces ofthe flanges, wherein the flanges are each constituted by a disc integralwith an end of the driven pinion, the discs and the driven pinion beingconcentric, the discs covering the teeth of the driven pinion.
 2. Gearpump according to claim 1, wherein the flanges act as guides for therotation of the driven pinion.
 3. Gear pump according to claim 1,wherein the means for exerting a pressure on the external faces of theflanges of the discs comprise a first and a second space between theexternal faces of the discs and the bottom of the cavity provided in thepump body and in the cover respectively, and in which are appliedapproximately identical pressures.
 4. Gear pump according to claim 3,wherein a canal crosses the driven pinion from one end to the other, sothat the first and second spaces are made to communicate with eachother.
 5. Gear pump according to claim 3, wherein the first and secondspaces are made to communicate with the discharge zone of the pump. 6.Gear pump according to claim 5, wherein a canal or a groove is providedso that the discharge zone of the pump is made to communicate with atleast one of the spaces.
 7. Gear pump according to claim 1, wherein thediscs are hollowed out.
 8. Gear pump according to claim 4, wherein thefirst and second spaces are made to communicate with the discharge zoneof the pump.
 9. Gear pump according to claim 8, wherein a canal or agroove is provided so that the discharge zone of the pump is made tocommunicate with at least one of the spaces.
 10. Gear pump according toclaim 2, wherein the means for exerting a pressure on the external facesof the flanges of the discs comprise a first and a second space betweenthe external faces of the discs and the bottom of the cavity provided inthe pump body and in the cover respectively, and in which are appliedapproximately identical pressures.
 11. Gear pump according to claim 10,wherein a canal crosses the driven pinion from one end to the other, sothat the first and second spaces are made to communicate with eachother.
 12. Gear pump according to claim 10, wherein the first and secondspaces are made to communicate with the discharge zone of the pump. 13.Gear pump according to claim 12, wherein a canal or a groove is providedso that the discharge zone of the pump is made to communicate with atleast one of the spaces.
 14. Gear pump according to claim 11, whereinthe first and second spaces are made to communicate with the dischargezone of the pump.
 15. Gear pump according to claim 14, wherein a canalor a groove is provided so that the discharge zone of the pump is madeto communicate with at least one of the spaces.
 16. Gear pump accordingto claim 2, wherein the discs are hollowed out.
 17. Gear pump accordingto claim 3, wherein the discs are hollowed out.
 18. Gear pump accordingto claim 4, wherein the discs are hollowed out.
 19. Gear pump accordingto claim 5, wherein the discs are hollowed out.
 20. Gear pump accordingto claim 6, wherein the discs are hollowed out.